The present invention relates to techniques for forming, from a pourable material such as liquid concrete, pre-cast, re-enforced panels used in prefabricated building construction, and more particularly to mold apparatus that can support pre-cured panels for lifting and transporting to a drying station where a number of the panels can be vertically stacked for controlled curing.
The advantages of concrete construction for buildings has long been known. Those advantages include high fire ratings, seismic resistance, and pertinent here, use for prefabricated building construction in which a structure's constituent wall section panels may be pre-cast at one location and transported to the building site for assembly when needed.
However, prefabricated construction is not without its disadvantages. Conventional techniques use horizontally placed forms for forming panels. Reinforcement bars are placed in the form, and liquid concrete, or other pourable material, introduced into the form, and left to cure--which can take upwards of 18 hours or more, depending upon the ambient environment in which the pre-casting takes place. In addition to precluding use of the form until the panel has cured sufficiently to have the structural integrity to be moved, the space itself is rendered unavailable until the panel cures. Further, the drying panels are often left exposed to direct sunlight to cause them to hydrate at an uneven rate. For this reason drying panels are periodically watered to effect a more even drying, which may prevent uneven drying, but lengthens the time for the panel to fully cure.
To attempt to alleviate these and other problems, a number of proposals have been put forward to enhance the curing process, including the use of chemical additives such as cure accelerators, varying the mix ratios of the pourable material used, or steam curing the panels, all of which add to the cost of manufacture both in terms of monetary expense and labor. As a result, pre-cast panels are not used as much as would be in building construction if panel manufacture cost and/or cycle times were not what they are.
Thus, as can be seen, improved pre-cast manufacture techniques that can decrease the manufacture cycle time are needed in order to take advantage of the advantages offered by prefabricated construction.